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Yonaguni Island Underwater Ruins

Japan / Okinawa / Ishigaki /
 monument, underwater, interesting place, draw only border

The Yonaguni Monument is a massive underwater rock formation off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan. There is a debate about whether the site is completely natural, is a natural site that has been modified, or is a manmade artifact.

The sea off Yonaguni is a popular diving location during the winter months owing to its large population of hammerhead sharks. In 1987, while looking for a good place to observe the sharks, Kihachiro Aratake, a director of the Yonaguni-Cho Tourism Association, noticed some singular seabed formations resembling architectonic structures. Shortly thereafter, a group of scientists directed by Masaaki Kimura of the University of the Ryūkyūs visited the formations.

The formation has since become a relatively popular attraction for divers despite the strong currents. In 1997, Japanese industrialist Yasuo Watanabe sponsored an informal expedition comprising writers John Anthony West and Graham Hancock, photographer Santha Faiia, geologist Robert Schoch, a few sport divers and instructors, and a shooting crew for Channel 4 and Discovery Channel. Another notable visitor was freediver Jacques Mayol, who wrote a book on his dives at Yonaguni.

The Monument consists of medium to very fine sandstones and mudstones of the Lower Miocene Yaeyama Group believed to have been deposited about 20 million years ago. Most of the formations are connected to the underlying rock mass (as opposed to being assembled out of freestanding rocks).


The formation called "The Turtle"
The main feature (the "Monument" proper) is a rectangular formation measuring about 150 by 40 m (490 by 130 ft) and about 27 m (90 ft) tall; the top is about 5 m (16 ft) below sea level.

Some of its details are said to be:

Two closely spaced pillars which rise to within eight feet of the surface;
A 5 m (16 ft) wide ledge that encircles the base of the formation on three sides
A stone column about 7 m (23 ft) tall
A straight wall 10 m (33 ft) long
An isolated boulder resting on a low platform;
A low star-shaped platform;
A triangular depression with two large holes at its edge;
An L-shaped rock.
Nearby cities:
Coordinates:   24°25'55"N   123°0'44"E
This article was last modified 6 years ago